[CCoE Notice] PhD Defense: Selectivity and spatiotemporal features of sorption and oxidation in monolith and packed bed reactors

[Hutchinson, Inez A]

PhD DEFENSE STUDENT: Oxford Po-Yu Peng

DATE: Thursday, July 26, 2018

TIME: 2:00 PM

PLACE:  Mechanical Engineering Large Conference Room

DISSERTATION CHAIRs: Dr. Michael Harold and Dr. Dan Luss

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TITLE:
Selectivity and spatiotemporal features of sorption and oxidation in monolith and packed bed reactors

This dissertation involves three studies. The first investigates the spatiotemporal features of zeolite-containing diesel oxidation catalyst. The second was of coupled HCs desorption on the zeolite beta. The third investigates the performance of oxidative coupling of methane on Na/Mn/W/SiO2 catalyst.
The first study was of influence of BEA on the performance of the HC (ex. n-dodecane) light-off (LO) and of the transient HC oxidation. This study required measurements of the spatiotemporal features of zeolite-containing diesel oxidation catalyst. These spatially-resolved measurements were conducted by combining Spaci-MS and c-OFDR to provide unparalleled detail of the heterogeneous catalytic reaction.
Steady-state experiments revealed unexpected periodic oscillations of CO2 and temperature in a feed temperature range of (142-181 oC). A low dimensional model describing the ‘tug-of-war’ coupling mechanism between oxidation and sorption was developed, that fit a series of kinetic experiments. The model predicted the experimentally observed periodic oscillation of CO2 formation. The model successfully predicted the observed spatio-temporal experimental behavior and provides a general insight about the oscillation occurrence.
There is interest in gaining insight and understanding of coupled HCs desorption on the zeolite Beta. Thus. we co-adsorbed a ternary mixture of n-hexane, toluene, and propylene on zeolite beta and studied their desorption. Temperature programmed desorption experiments revealed that a second and higher temperature hexane desorption peak occurred in a propylene co-feed. To explain the observations a mechanism was proposed that hexane desorption was inhibited by low concentration of weakly adsorbing propylene concentration while inhibition attributed to propylene blockage of hexane transport. The new insight about the coupling may enable development of a new strategy to improve hydrocarbon uptake and release for emission control devices.
The oxidative coupling of methane (OCM) has recently motivated significant industrial and academic studies of how to enhance the yield of the oxidized products. The third study was enhancing this yield by post-OCM reactions. This experimental study consisted of feeding simulated OCM products on a Na/MN/W/SiO2 catalyst at elevated temperature. The experiments revealed that the post-OCM reactions produce additional valuable C2+ at the moderate reaction condition (~1025 oC and 2 Bar) C2+ yield was greatly improvement from 22 to 27%, showing the importance of heat effects and feasibility of the new strategy in promoting OCM catalyst performance. This finding provides a new method to enhance C2+ production in an OCM reactor by optimizing the pressure and temperature distribution along the axis.
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